This study seeks to take a closer look at how to create a reliable and repeatable method for comparative measurement and analysis of comfort regarding vibrations in strollers.To achieve this goal the study has been divided in three questions that focuses on established standards and previous studies, a construction of a measurement method and finally a construction of a data analysis method. To answer these questions the study uses information gathered from a literature study, conducted experiments as well as an analysis of quantitative data via descriptive statistics and thematic analysis. Furthermore, during the development of the comparative method the authors has made use of various workshops to generate ideas and evaluate the best course of action. This has allowed for rapid iteration of the method that is presented in this report.To make a comparison with previous studies possible, ISO-2631:1, ISO-102361:1 and the Swedish Work Environment Authority’s regulations regarding whole body vibration are used as a foundation for the decisions made. The final method is presented in its entirety, both regardingmeasurement and data analysis. This study also displays an example of how both methods can be used to compare strollers.Additionally, the report applies the developed method on a selection of Thules’ and their competitors’ strollers. For the purpose of anonymity, the strollers’ brand and names has beenreplaced with code names and taken pictures has been replaced by illustrations.Finally, the results of the report is analyzed and discussed to compare the decisions taken throughout the process with each other as well as with the current standards, regulations and previous studies. Moreover, a conclusion in made that the presented methodology is a fair toolfor measurement of the passengers’ comfort with regard whole body vibrations in strollersduring activity. The resulting data is directly comparable on a case-by-case basis, but caution is advised if comparisons are to be made with the guidelines provided in presented standards or the regulations regarding whole body vibration, as these are not adapted for measurementsconducted with children.

This study quantifies whole-body vibration on a range of mine machinery typically used in a South African open cast mine. The ISO 2631-1 (1997) standard was used in the computation of weighted root mean square (WRMS) and vibration dose values (VDVs) whereas the ISO 2631-5 (2004) standard was used in the computation of daily static compressive stress (Sed) and R factor values. Two methods have been used to evaluate the whole-body vibration on a wide range of equipment used in an open cast mine. There are two main parameters for each of the standards. The ISO 2631-1 (1997) standard utilises the daily exposure A(8) and VDV, whereas the new ISO 2631-5 (2004) standard methodology uses the parameters Sed and R factor. ISO 2631-1 (1997) is poor in taking account of transient shocks. This led to the development of ISO 2631-5 (2004). Signals were therefore generated in the laboratory to further explore the parameters of the two standards. Vibration signals of more-or-less steady periodic processes can be approximated by superposition of sinusoids. To investigate the effect of shocks on the WBV response parameters used in the two standards, a series of investigations were conducted using very simplified simulations to capture the essential nature of various operational conditions, and qualitatively explain the trends in the response parameters. Pure sinusoidal data was first generated without shocks and investigated. Subsequently, sinusoidal signals with higher amplitudes were generated and investigated. Sinusoidal signals with increasing shock amplitude up to and exceeding the crest factor of 9 based on ISO 2631-1 (1997) were generated and analyzed. Finally, simulated data with different shock magnitude for five typical example cases were then generated and analyzed. The pure sinusoidal data was artificially generated using the signal generator at different amplitudes and frequencies, which are similar to field observed frequencies to enable numerical investigation of parameters to be carried out. A subset of the data was selected based on frequencies and amplitudes obtained on the field so as to have a representative data set on which investigations were carried out. The two parameters of the two standard methodologies were computed using simulated sinusoidal signal data. The trends in each of the parameters corresponding to each of the standards were monitored using various scenarios obtained by varying the signal parameters and compared against each other. There was approximate proportional correlation between the two parameters (VDV and Sed) with varying degrees of slope for each scenario. The Sed and VDV parameters are plotted on the x- and y-axes respectively. The graphs with slope greater than 1 corresponded to signals with low or no shock content; whereas the graphs with slope less than 1 corresponded to high shock content. The shock parameters (VDV and Sed) corresponding to the ISO 2631-1 (1997)and ISO 2631-5 (2004) standard methodologies were computed from field data and compared to see if the same trend obtained from the numerically obtained sinusoidal signals could be validated. It was found that the there was a gradual band correlation with slope less than 1 between the VDV and Sed parameters corresponding to signals of high shock content thereby validating the numerical findings. Since little or no extensive epidemiological studies have been carried out on the new methodology; it is recommended that more epidemiological studies be done to determine the exposure action and exposure limit values with respect to shocks in the Sed parameter for the new ISO 2631-5 (2004) standard methodology. It is advisable that caution is taking when using the new ISO 2631-5 (2004) standard methodology in evaluating whole-body vibration measurements until the limits are properly established. It is suggested that the new standard be used along with the established ISO 2631-1 (1997) standard methodology. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Mechanical and Aeronautical Engineering / Unrestricted

High speed in waves, necessary in for instance rescue or military operations, often result in severe loading on both the craft and the crew. To maximize the performance of the high-speed craft (HSC) system that the craft and crew constitute, balance between these loads is essential. There should be no overload or underuse of crew, craft or equipment. For small high-speed craft systems, man is often the weakest link. The human exposure to vibration and shock results in injuries and other adverse health effects, which increase the risks for non-safe operations and performance degradation of the crew and craft system. To achieve a system in balance, the human acceleration exposure must be considered early in ship design. It must also be considered in duty planning and in design and selection of vibration mitigation systems. The thesis presents a simulation-based method for prediction and evaluation of the acceleration exposure of the crew on small HSC. A numerical seat model, validated with experimental full-scale data, is used to determine the crew's acceleration exposure. The input to the model is the boat acceleration expressed in the time domain (simulated or measured), the total mass of the seated human, and seat specific parameters such as mass, spring stiffness and damping coefficients and the seat's longitudinal position in the craft. The model generates seat response time series that are evaluated using available methods for evaluation of whole-body vibration (ISO 2631-1 \&amp; ISO 2631-5) and statistical methods for calculation of extreme values. The presented simulation scheme enables evaluation of human exposure to vibration and shock at an early stage in the design process. It can also be used as a tool in duty planning, requirements specification or for design of appropriate vibration mitigation systems. Further studies is proposed within three areas: investigation of the actual operational profiles of HSC, further development of seat models and investigation of the prevailing injuries and health problems among the crew of HSC. / <p>QC 20150126</p>